<HTML><HEAD><TITLE>viewable_element(++ViewableName, ++IndexList, ?ViewableElement)</TITLE>
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<H1>viewable_element(++ViewableName, ++IndexList, ?ViewableElement)</H1>
Index a viewable element inside a viewable.
<DL>
<DT><EM>ViewableName</EM></DT>
<DD>Atom: name of an existent viewable.
</DD>
<DT><EM>IndexList</EM></DT>
<DD>List of integers: the coordinates of the viewable element within the viewable.
</DD>
<DT><EM>ViewableElement</EM></DT>
<DD>Term to be unified with the viewable element.
</DD>
</DL>
<H2>Description</H2>
Note that this predicate throws an error if there are no current visualisation clients. Retrieves a single viewable element from a named viewable, given the element's array coordinates, and unifies it with <em>ViewableElement</em>. IndexList must be a ground list which has one positive integer for each dimension of the viewable.
<H3>Fail Conditions</H3>
ViewableName is not instantiated to the name of an existent viewable. ViewableElement will not unify with the specified element.
<H3>Resatisfiable</H3>
no
<H3>Exceptions</H3>
<DL>
<DT><EM>(1) general error </EM>
<DD>There are no current visualisation clients
<DT><EM>(4) instantiation fault </EM>
<DD>ViewableName is not an atom or string
<DT><EM>(5) type error </EM>
<DD>IndexList is not a ground list of integers
<DT><EM>(6) out of range </EM>
<DD>A co-ordinate in Index is out of range
<DT><EM>(8) bad argument list </EM>
<DD>IndexList has the wrong number of elements
</DL>
<H2>Examples</H2>
<PRE>       Success:

       Failure:

       Exceptions raised:
</PRE>
<H2>See Also</H2>
<A HREF="../../lib/viewable/viewable_create-3.html">viewable : viewable_create / 3</A>, <A HREF="../../lib/viewable/viewable_size-2.html">viewable : viewable_size / 2</A>, <A HREF="../../lib/vc_support/viewable_element_to_string-2.html">viewable_element_to_string / 2</A>, <A HREF="../../lib/vc_support/viewable_element_execute-3.html">viewable_element_execute / 3</A>
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